Constructional element

ABSTRACT

In constructional elements comprising two parallel plates of nailable material and one or more webs of elongated sinuous metal sheeting extending edgewise between the plates and having teeth at the edges driven into the plates for keeping them together, the sheet herein is formed at the teeth locations with a sharp bend which extends transversely of the sheet throughout its width and further into the tooth so as to provide a common stiffening of teeth and web at these locations. At the edges of the web sheet the teeth should be placed directly opposite each other. The teeth have parallel side edges extending outwardly from their base to a pointed end portion with one or more points. When using two or more points the web is formed with a separate sharp bend for each point. Between the shaped teeth also smaller flat teeth may be formed at the edges of the web sheet. Curved structures are made by separately curving the plates and the web before assembly. For stiffening the structure in longitudinal and transverse planes, two sets of web sheets are provided which extend in directions at right angles to each other and are interconnected in plane contact in portions forming 45* with the main directions. For large elements, adjacent plate sections are jointed by means of a separate sinuous sheet with teeth at the edges. Where different moisture conditions on the opposite sides of the element are expected, the plates are separately conditioned in moisture content before assembly. Web sheets extending along the edges of the plates may be formed with aligned plane portions separated by sharp channel-shaped bends at which the teeth are located. Adjacent elements may be locked against relative vertical displacement by means of matching tongues and slots in fittings attached to web sheets at the edges of the elements. Watertight elements, such as elements of floating structures are made by forcing the edges of web sheets extending along the edges of the element into sealing engagement with the plates and sealingly jointing these sheets.

[ 1 Mar. 25, 1975 1 CONSTRUCTIONAL ELEMENT [76] Inventor: Johan Caspar Falkenberg,

Fjordveten 59c, N-l322 Hovick, Norway 22 Filed: Jan. 30, 1973 21 Appl. No.: 327,924

[30] Foreign Application Priority Data June 29, 1972 Norway 2328/72 Jan. 31, 1972 Norway 228/72 [52] US. Cl 52/618, 52/650, 85/11, 85/13 [51] Int. Cl. F046 2/26 [58] Field of Search 52/618, 615, 696, 650, 52/630, 620, 582, DIG. 6, 616; 85/11, 13, 14

[56] References Cited UNITED STATES PATENTS 2,377,169 5/1945 Mohr v 85/11 3,072,227 1/1963 Baker... 52/582 3,431,810 3/1969 Black.... 85/11 3,485,518 12/1969 Heise 52/14 X 3.538.668 11/1970 Anderson 52/615 3,591,210 7/1971 Heise 85/13 X 3,736,718 6/1973 Sylvan 85/14 X FOREIGN PATENTS OR APPLICATIONS.

1,269,175 1/1961 France ..-52/6l5 Primary E.\'aminerFrank L. Abbott Assistant Examinew-Carl D. Friedman Attorney, Agent, or Firm-Watson, Cole, Grindle & Watson [57] ABSTRACT In constructional elements comprising two parallel plates of nailable material and one or more webs or elongated sinuous metal sheeting extending edgewise between the plates and having teeth at the edges driven into the plates for keeping them together, the sheet hereinis formed at the teeth locations with a sharp bend which extends transversely of the sheet throughout its width and further into the tooth so as to provide a common stiffening of teeth and web at these locations. At the edges of the web sheet. the teeth should be placed directly opposite each other. The

teeth have parallel side edges extending outwardly from their base to a pointed end portion with one or more points. When using two or more points the web is formed with a separate sharp bend for each point. Between the shaped teeth also smaller flat teeth may be formed at the edges of the web sheet. Curved structures are made by separately curving the plates and the web before assembly. For stiffening the structure in longitudinal and transverse planes, two'sets of web sheets are provided which extend in directions at right angles to each other and are interconnected in plane contact in portions forming 45 with'the main direc tions. For large elements, adjacent plate sections are jointed by means of a separate sinuous sheet with teeth at the edges. Where different moisture conditions on the opposite sides of the element are expected, the plates are separately conditioned in moisture content before assembly. Web sheets extending along the edges of the plates may be formed with aligned plane portions separated by sharp channelshaped bends at which the teeth are located. Adjacent elements may be locked against relative vertical displacement by means of matching tongues and slots in fittings attached to web sheets at the edges of the ele ments. Watertight elements, such as elements of float ing structures are made by forcing the edges of web sheets extending along the edges of the element into sealing engagement with the plates and sealingly jointing these sheets.

7 Claims, 19 Drawing Figures 1 CONSTRUCTIONAL ELEMENT BACKGROUND OF THE INVENTION The invention relates to constructional elements of the kind comprising two plates of nailable material and at least one web which keeps the plates in spaced parallel positions. The material of the plates may be solid wood, for example sawed boards, or plywood, chipboard, wood fibre board or the like. Elements of the said kind may be made with one, two or more webs and also be of various design in other respects, for example as l-, H- or box beams or as larger elements adapted for various purposes. In particular such elements are used in the form of so-called stressed-skin elements as loadsupporting floor and roof elements, mostly of closed, box-like shape and filled with insulating material, in which case the webs are most frequently constituted by wood beams to which the plates are nailed and/or glued so as to form upper and lower beams in the structure.

However, it is also known to make elements of the kind mentioned above with webs in the form of elongated sinous metal sheets, preferably steel sheets, which along the lateral edges are formed with pointed teeth which are pressed into the plate members. A structure of this kind is disclosed in the German pub lished patent specification No. 1,004,790 of 1954. In the form shown and described in that publication this concept, however, is of little practical interest, the attachment of the web sheet in the plate affording little resistance to separating forces and, for such reason, the plates must be held together by bolts passing therethrough.

In the U.S. Pat. No. 3,538,668 it has been proposed to increase the pull-out force, i.e. the resistance of the teeth to being pulled out of the plates, by bending the teeth alternately to opposite sides like the teeth of a saw blade, so that, when pressed in, they will be further deflected so as to be locked in the wood plate. At the same time it is proposed to reinforce the teeth locally by giving them an angular cross-sectional shape. However, in this case the teeth are subjected to considerable bending during assembly, so that they must be made very short in order not to break. Especially with hard fibre board and chipboard of qualities at present manufactured as floor boards, it has turned out to be very difficult to achieve a satisfactory connection in this manner with the use of economically justifiable steel qualities and thicknesses.

SUMMARY OF THE lNVENTlON The present invention is concerned with constructional elements of the type disclosed in aforementioned patents, the element comprising two plates of nailable material and at least one web which keeps the plates mutually spaced in parallel positions, and comprises an elongated sinous metal sheet extending edgewise between the plates and engaging the same with teeth formed in its lateral edges and pressed into the respective plates, and a main object of the invention is to enable the web to keep the plates better together as compared to known structures.

The solution of this problem is based on the following considerations.

The force required for pressing a peg or tooth into wood or similar material will be the sum of the force causing the tooth to cut through the wood fibres, and

the frictional force acting on the lateral faces of the tooth. For a given width of the tooth the cutting force will be approximately constant and independent of the insertion depth. The frictional force, however, will increase with the length of the tooth pressed in. Thus. the pressing force will increase with the depth of insertion. When the tooth is pulled out only the frictional force is effective, which is equal to the final pressing force minus the constant cutting force. Hence, the pull-out force to be expected will increase linearily with the pressing force.

From this viewpoint it is desirable to shape the web sheets and teeth in such a manner as to permit the maximum pressing force to be used, or with other words, that for a plate material of a given nailing hardness there can be used teeth having the maximum length possible without being broken when pressed in.

With web sheets and teeth of optimum shapes in this respect it will also be possible to use a minimum sheet thickness for a given plate material and a given value of the pull-out force of the teeth. This has obvious advantages with respect to economy and weight and may, where heat insulating elements are concerned, be of decisive importance, the heat loss through the web sheet being proportional to its thickness, so that a thicker web sheet may reduce the insulating capacity of the element to a level which in many cases is not acceptable.

The invention aims at providing shapes of web sheets and teeth which constitute an optimum based on these considerations, or in other words, afford a maximum utilization of the sheet material. This is primarily achieved due to the fact that in places where teeth are located the sheet is formed with a sharp bend extending throughout its width and further out through the teeth, which are preferably located directly opposite each other, so that web sheet and teeth will have a common stiffening sectional shape aligned in the direction of insertion. Due to this shape the teeth and the web sheet are reinforced against buckling, and it is ensured that the pressing forces will act substantially rectilinearly through teeth and sheet. Thereby it becomes possible in the first place to make the teeth longer without the risk of breaking and undue deflection, and in the second place the sheet is enabled to resist an increased compressing force without buckling or bending locally in the areas where the teeth are placed. A third advan tage achieved by forming the web sheet with a straight continuous sectional shape is that the shaping tool for the web sheet can be formed simply by planing, and that the same tool can be used for several widths ofweb sheets.

With a view to increasing the pull-out force by increasing the frictional force and at the same time further increasing the stiffness of the teeth, the invention further teaches to form the teeth with lateral edges extending in the pressing direction from its base to a pointed end portion.

Further, such teeth may conveniently be formed with at least two points so as to permit the use of larger and stiffer teeth with consequent increased pull-out force and shear resistance. In that connection it may also be convenient to form web sheet and tooth with at least two sharp bends in alternate directions, so as to provide a separate local stiffening for each point.

In constructional elements according to the invention the web sheets may be arranged in many different ways,

for example as indicated in the preamble and/or as disclosed in the prior publications referred to. For example for elements of box-like shapes it may be of particular interest while using a pull-out force affording safe resistance to separation, to make the elements with a water-tight space between the plates by forcing web sheets extending along all edges of the plates into sealing contact with these, and also to provide sealing joints for the sheets, for example by welding, riveting, seaming, deformation jointing or the like. Further, in elements of considerable two-dimensional size in the plane of the plates it may be of interest to use webs with crossing main directions, make the plates composed of two or more sections and/or provide for jointing of adjacent elements.

These and additional features and advantages of the invention will become apparent from the following description of the invention when considered in conjunction with the accompanying drawings.

IN THE DRAWINGS FIG. I is a perspective view showing part of an embodiment of the constructional element,

FIG. 2 is a perspective view on a larger scale showing part of a web sheet capable of forming part of the element in FIG. 1,

FIGS. 3-5 are perspective views of alternative tooth shapes,

FIGS. 6ac are partial views in cross-section taken transversely to the web sheet in FIG. 2, and illustrate three stages of an assembling process during which the teeth are forced through a plywood plate and clinched on the opposite side,

FIG. 7 is a diagrammatic view on a small scale of a constructional element according to the invention of a substantially plate-shape design with stiffening in two directions, I

FIGS. 8 and 9 are sectional views taken along the lines 88 and 99, respectively, in FIG. 7,

FIGS. 10 illustrates a detail of the element in FIG. 7-9 in horizontal section and on a larger scale,

FIG. 11 is a plan view of part of a blank for a web sheet of another embodiment of the invention,

FIGS. 12 and 13 are end views showing portions of two web sheets made from the blank in FIG. 11,

FIGS. 14 and 15 are views corresponding to FIG. 11 and FIG. 12 or 13, respectively, of a still further embodiment of the web sheet,

FIG. 16 is a sectional view taken along line 1616 of FIG. 17 showing ajointing sheet adapted to be used for the forcetransmitting connection of two pairs of plate sections forming part ofa constructional element according to the invention,

FIG. 17 is a sectional view taken along line 17-17 of FIG. 16,

FIG. 18 is a detail view in horizontal section along the line l8l8 of FIG. 19 of part of a constructional element according to the invention in the form ofa closed box element with facilities for connecting elements placed side by side, and

FIG. 19 is an elevational view of the same.

The constructional element in the embodiment shown in FIG. 1 is in the form ofa box-shaped beam 1. The beam comprises an upper plate member 2, a lower plate member 3 and two corrugated web sheets 4 interconnecting the plates. The plate members may for example be of chipboard or plywood with a thickness of l025 mm. The web sheets may be of steel with a thickness of 0.5-1.2 mm. A design as shown in FIG. 1 may conveniently be used as beams in tiers for floors and roofs in buildings, and the upper plate member may therefore be formed with a groove 15 in each longitudinal edge, so that the element can be connected to an adjacent element by a groove and feather connection.

In FIG. 2 there is shown a convenient shape of the web sheets of the element in FIG. 1. The sheet 4 is sharply folded into zig-zag shape about parallel transverse fold lines 6. At the longitudinal edges there are punched teeth 5 with axes coinciding with those of the fold lines so that the teeth achieve a folded shape corresponding to that of the body of the sheet. The tooth has parallel or slightly converging side edges 7 and terminates in a point 8 so as to be capable of being pressed into the material of the plate member.

A tooth shape as shown affords a stiffness many times that of a plane tooth. For example it may be mentioned that with a sheet thickness of 0.7 mm, a tooth width of 5.6 mm and a fold angle of the bending resistance will be four times as high, which means that the shaped tooth may be made about twice as long as a plane tooth without increased risk of breaking when pressed in. Since the pullout force may here be reckoned as proportional to the length of the parallel side edges, the tooth point not contributing to any considerable extent, it will be clear that a doubling of the total length of the tooth will result in more than a doubling of the pull-out force, and that the ratio will be higher with increased hardness of the material of the plate members and correspondingly reduced permissible length of the teeth. Due to the fact that the fold line from the tooth is continued throughout the entire width of the web sheet, the latter will at the same time be well suited for resist ing the increased local buckling stresses caused by the increased pressing force required for affording the increased pull-out force.

It may be mentioned that in particular with chipboard of qualities used at present it has turned out to be impossible in practice to provide a satisfactory beam structure as shown in FIG. 1 with a reasonable thickness of the web sheet without shaping the same in accordance with the invention.

FIG. 3 shows a tooth shape which is particularly convenient for pressing into hard materials. The tooth is formed with a double point, the objectof which in the first place is to make the pressing force on the tooth during assembly act substantially in the centre of gravity of the tooth cross-section and therefore not to induce substantial bending of the tooth. Secondly the two points afford a better guiding and resist twisting of the tooth, and thirdly, with the same point angle and total tooth length, the shape shown results in a somewhat longer portion with parallel lateral edges, which again affords an increase of the pull-out force for the reasons earlier explained.

FIG. 4 shows a tooth shape having a continuous oblique terminal edge 110. Due to the fact that in this case the tooth point 111 will have an excentric position relative to the axis of the tooth, the tooth will, when pressed in, have a tendency to be deflected toward the side at which the point is located, and by forming the teeth with points alternately on one side and the other there will be achieved a locking effect of the points pressed into and deflected in the wood material. This tooth shape may be convenient when it is desired to avoid pressing of the tooth through the entire thickness of the wood plate, for example when the latter is relatively thick. It will be appreciated that in this case the deflection takes place consequent to the asymmetry of the tooth point, and that the tooth is originally straight and is not subjected to bending in the portion located outside the plate material.

The tooth shape shown in FIG. 5 may be convenient when the tooth is to penetrate through a relatively thin plate and it is at the same time desired to have a certain width at the base of the tooth with a view to high shear resistance.

In FIGS. 6a-c it is shown how the teeth 102 are pressed into and through a wood plate, for example a plywood plate 108. FIG. 6a shows a tooth pressed halfway into the plate. In this case the tooth 102 is shown with a point of symmetric shape similar to that in FIG. 2, but with the point 103 bent slightly inwardly of the center of gravity of the tooth as shown in FIG. 6a. Due to this shape it is obtained that when encountering the backing steel 109 in the press, the tooth will be clinched further inwardly so that the point 103 will penetrate back into the plate 108 as shown in FIGS. 6b and 6c. This results in an increase of the pull-out force on the tooth, apart from the fact that projecting points are avoided.

FIGS. 7-10 illustrate a so-called stressed-skin element 120 comprising two parallel wood plates 121, 122 interconnected by both longitudinal and transverse web sheets 123 and 124, respectively, preferably of a shape as shown in FIG. 2. For facilitating the illustration the corrugation of the web sheets has not been shown in FIGS. 79. The longitudinal sheets 123 are shown to be continuous in FIG. 10, whereas the transverse sheets 124 are divided into sections which at the intersections are connected to the sheets 123 in known manner, preferably by spot welds 125 or by rivets. The connection may also be provided as a deformation joint by means of fixing tongs.

The structure 120 is a so-called two-way element, i.e. an element having a considerable transverse dimension and stiffened in both longitudinal and transverse planes, and for this purpose the individual sections of which the web sheets 124 are composed have to be interconnected for transmitting vertical forces (shearing forces). This will for example be the case at the intersection I26 in FIG. 10.

The web sheets 123, 124 may typically consist of galvanized steel sheeting with a thickness within the range 0.5-1.0 mm.

When making a plate-shaped element structure 120, the corrugated web sheets 123, 124 are at first placed in desired relative positions on the lower plate member 121 and interconnected at intersections as described above. Thereafter the upper plate 122 is placed in position, and the whole is inserted into a suitable press which then presses the plates 121, 122 against each other so that the teeth of the web sheets penetrate into them, and, if they are of such a length as to penetrate through the wood plates, are clinched as explained above.

In order to ensure exactly parallel positions of the two wood plates 2 and 3 or 121 and 122, respectively, several distance blocks cut to dimensions corresponding to the desired spacing of the wood plates may be placed on the lower plate so as to prevent the web sheets from being pressed in farther than what they are designed for. However, this will not be necessary if the movement of the plates of the press are exactly controlled with respect to parallelism and stroke length.

When the teeth are pressed straight through the plates and clinched as described above, it is possible to have a good visual check on correct assembly.

An element of plate-shaped design as shown in FIGS. 7-10 can be manufactured in factories and used for several different purposes, such as self-supporting floor and roof elements in buildings, shuttering plates for concrete structures, such as ceilings and walls, loadsupporting tiers in bridges etc. The web sheets lend themselves easily to curving in the horizontal plane and are therefore well suited for use in curved beam and plate structures.

FIGS. 11-15 illustrate further shapes of teeth and sheets. With the simple V-shape of the teeth shown in FIGS. 25 there are certain limits for the tooth width which can be permitted without the free edges becoming unstable and bulging when pressed in. Several experiments have shown that the total width of teeth of shapes as shown in FIGS. 25 ought not to exceed about sixteen times the sheet thickness. However, it is often desirable to increase the width considerably over this in order to achieve a greater shear and pull-out re sistance of each tooth, and, if so, the tooth may be made with more fold lines and, if desired, with more points as shown-in FIGS. 11-15. As in FIG. 2 the teeth 11] in FIG. 11 and 141 in FIG. 14 are assumed to be formed directly opposite each other at the lateral edges of the sheet. The common axis 110, which extends at right angles to the longitudinal direction of the sheet, will after a shaping into Wform as shown in FIG. 12 form a continuous fold line 110 forming the central axis of the tooth section and extending straight through the web sheet and into the opposite tooth. Such W- formed sectional shape will in addition to permitting-a greater tooth width afford a better torsional stability than a V-shape since the shear center of the tooth cross-section will be located at or near the center of gravity.

Teeth of Z-formed sectional shape as shown in FIG. 13 may be convenient if it is desired to form a web sheet with a more shallow corrugation with the same punching tool as used for FIG. 11.

In FIG. 14 there is shown a form in which the teeth has three points and the base portion between the teeth is formed with small teeth 142 which remain plane after the shaping of the sheet. This is a convenient form when it is desired to make sealed elements in which even the base portion between the teeth is to be pressed somewhat into the plates. If the latter are of plywood, the teeth 142 will cut more easily through the outermost veneer layer and prevent cracking of portions of the same away from the adjacent layer consequent to the very concentrated surface pressure from a perfectly straight base portion.

The shape in FIG. 15 may be formed in a blank as shown in FIG. 14. As will be seen, in this case the sheet has aligned plane portions separated by sharp inward bends formed symmetrically with respect to transverse planes through the respective central lines 140 of the teeth. This shape is particularly suited for the outer web sheets in an element as shown in FIG. 18, since in that case there is obtained a maximum overall aligned sheet area affording increased freedom in attaching connecting fittings and less problems with sealing and insulation between adjacent and constructional elements.

FIGS. 16 and 17 show the manner of using a wave shaped metal sheet 161 with large teeth 162 and 162 for providing a force-transmitting connection of two sections of aplate member. If for example poywood is used as the plates it will be necessary in large elements to make up the plates by jointing individual plates of suitable standard sizes. For this purpose the joint must be capable of resisting the pressure and shear forces in the plane of the plate which are caused by the bending stresses to which the element is subjected, and in most cases it is then necessary to resort to a glued bevel joint or a blunt joint with a jointing strip glued or-nailed to the inner face. These jointing methods are both timeconsuming and therefore expensive, and especially the glued bevel joint requires expensive special equipment.

With a joint in the form shown in FIGS. 16 and 17 it is not necessary to work the edges of the plates or manipulate the plates in addition to placing them in position on the web sheets. The jointing itself takes place conjointly with the assembling operation. The gap between the plates may be sealed afterwards, for example by pressing an elastic sealing strip of rubber or plastic into the gap. In FIG. 17 the base portion 167 between the teeth is shown to be pressed somewhat into the plate member, whereby this portion of the web sheet is stiffened so as not to buckle when transmitting compression forces.

The height of the corrugations of the web sheet 161 ought to be such that the teeth 162, 162 will have a sufficient spacing, for example -15 mm, from the edges of the plate members. In flat condition the teeth 162, 162 may have a shape as shown in FIG. 14 or have more than three points.

In FIG. 18 and 19 there is shown a portion of an entirely closed box-shaped element, in which sheets of the type shown in FIG. are used for the webs. These extend entirely around the element and are closed at the joint by a seam 187. An element of this form may be made entirely water-tight by using such a high pressure for the assembling that even the base portions of the web sheets are pressed somewhat into the plate members. This may be of considerable advantage by preventing water from penetrating into the element during the time of construction and causing consequent moisturc problems, for example risk of damage on the insulation.

Evenly spaced on the outer side of the web sheet 182 there are attached fittings 183 in the form of folded metal plates formed with a plane portion 188 preferably flush with the outer edges of the plate members. In this portion 188 there is formed a rectangular hole 185 and a corresponding tongue-shaped portion 184 capable of being bent outwardly about a line 190 so as to project at right angles to the plate 188. When two elements are place side by side the tongue-shaped portion 184 of one element can be passed into the hole 185 of the adjacent element and vice versa, and the two elements will thereby be locked together so as to be prevented from relative motions in the vertical direction, or in other words, there will be achieved a locking effect similar to that ofa groove and feather connection. Further, the fitting 183 may have additional holes 186 punched therein for attachment to a supporting base by hook bolts or the like and for attaching posts by means of flat steel strips.

At the corners of the element there may be mounted corresponding fittings 193 which in addition will serve for corner protection during transport and handling. The fittings 183 and 193 may be attached to the web sheets by spot welding, by rivets 189 or in other known manner.

It is well known that wood plates of the types used for purposes like the present ones are subjected to certain variations in their dimensions with variations in moisture content. If a plate-shaped element of a design as described is for example used as a floor element over a low service space in which the relative moisture content may be very high, the lower plate will be elongated relative to the upper one, which is located in a dryer indoor climate, and the element will adopt a downwardly convex curved shape. With a span of4 m this curvature may amount to as much as 10-15 mm and hence be inconvenient.

However, this effect can be considerably reduced if, before the element is pressed, each of the plates is conditioned to a moisture content constituting a medium value of the moisture content to be expected in the plate concerned in use. In use the element will there fore have a fairly even medium condition and only undergo moderate bendings up and down varying with the seasons and of an order that may normally be acceptable.

Although the elements made in accordance with the invention have been referred to as constructional elements and are described for use in horizontal tiers, of course nothing prevents the use of such elements in other parts of buildings, for example as wall elements. doors or gates, in bridgeelements, as deck elements and shutters in ships and as bottoms and walls for large cargo containers etc. Considering whathas been mentioned about the possibility of making the elements water-tight, it is also clear that such elements can be used in floating piers, pontoon bridges etc.

A closed, sealed box structure which in principle corresponds to the element described with reference to FIGS. 18 and 19, may also be made as a container, for example for liquids. The webs constituting the side walls should then in most cases be made higher relative to the width of the plates, and suitable charging and discharging means must be provided in cover, bottom or side-walls. The fittings 183, 193 may be provided with holes suitable for hoisting equipment. For the wall sheets the shape shown in FIG. 12 will be well suited because it affords better rigidity and strength for resisting liquid pressure than the shape shown in FIG. 15. For large containers the cover and bottom 181 and 181, respectively, may themselves be replaced by composite elements in accordance with the invention, for example of the type shown in FIGS. 68.

Although the element according to the invention has been described and shown as a plane element, the invention is not intended to be limited in this respect since nothing prevents the manufacture of for example cylindrically curved elements, which will be possible due to the corrugated shape of the sheet by stretching the sheet along one lateral edge before assembly so that the originally straight sheet is curved in its main longitudinal plane. Likewise, the plate members may be curved because of their elastic flexibility, and after compression the element will then have a curved permanent shape. Such elements may be used for curved roofs or as walls in silos.

What I claim is:

l. A construction element comprising two parallel plates of nailable material and at least one web element disposed between and perpendicular to said plates for interconnecting said plates in spaced apart relationship, said web element comprising an elongated sinuous metal sheet having a plurality of spaced teeth lying in the same plane as said sheet and extending outwardly of opposite side edges thereof, said teeth along one of said edges being in transverse alignment with the teeth along the other of said edges, said sheet having transverse, parallel and spaced sharp bends extending throughout its width and into said teeth, each said teeth having at least two sharp reverse bends extending likewise through the width of said sheet thereby forming teeth of Z-shaped cross-section.

2. The construction element according to claim 1 wherein each of said teeth have three sharp reverse bends extending likewise throughout the width of said sheet thereby forming teeth of W-shaped cross-section.

3. The construction element according to claim 1 wherein each of said teeth have three sharp reverse bends extending likewise throughout the width of said sheet thereby forming teeth of V-shaped cross-section.

4. The construction element according to claim 1, wherein said teeth have parallel side edges and sawtoothed terminal edges.

5. The construction element according to claim 1, wherein the opposite side edges of the web between said teeth have a saw-toothed configuration.

6. The construction element according to claim 1, wherein the width of said teeth as measured along the sinuous outline of the web is greater than their length.

7. The construction elementaccording to claim 1, wherein the depth of the tooth profile is substantially equal to that of the web. 

1. A construction element comprising two parallel plates of nailable material and at least one web element disposed between and perpendicular to said plates for interconnecting said plates in spaced apart relationship, said web element comprising an elongated sinuous metal sheet having a plurality of spaced teeth lying in the same plane as said sheet and extending outwardly of opposite side edges thereof, said teeth along one of said edges being in transverse alignment with the teeth along the other of said edges, said sheet having transverse, parallel and spaced sharp bends extending throughout its width and into said teeth, each said teeth having at least two sharp reverse bends extending likewise through the width of said sheet thereby forming teeth of Z-shaped cross-section.
 2. The construction element according to claim 1 wherein each of said teeth have three sharp reverse bends extending likewise throughout the width of said sheet thereby forming teeth of W-shaped cross-section.
 3. The construction element according to claim 1 wherein each of said teeth have three sharp reverse bends extending likewise throughout the width of said sheet thereby forming teeth of V-shaped cross-section.
 4. The construction element according to claim 1, wherein said teeth have parallel side edges and saw-toothed terminal edges.
 5. The construction element according to claim 1, wherein the opposite side edges of the web between said teeth have a saw-toothed configuration.
 6. The construction element according to claim 1, wherein the width of said teeth as measured along the sinuous outline of the web is greater than their length.
 7. The construction element according to claim 1, wherein tHe depth of the tooth profile is substantially equal to that of the web. 